Influence of notch radius and microstructure on the fracture behavior of Al–Zn–Mg–Cu alloys of different purity

The influence of notch radius on the fracture behavior of two high-strength Al–Zn–Mg–Cu alloys with different Fe content in the T73 condition was investigated. The fracture toughness tests were performed on non-fatigue-precracked notched bending specimens with different notch radii ranged from 0.15 mm to 1.0 mm. The obtained data were interpreted using the concept of Notch Fracture Mechanics combined with finite-element method (FEM) calculations. It was found that both alloys are very sensitive to the notch radius. The fracture toughness increases with increasing notch radius. For a given notch radii, the increase in fracture toughness is more significant for the more pure alloy. The fracture behavior of investigated alloys with respect to microstructural features and their relation with the fracture micromechanisms were analyzed.